Students fall in love with teachers? This is a wrong behavior in itself, regardless of age.
Students and teachers are intergenerational issues, regardless of age. As long as two people start to contact with each other in a teacher-student relationship, there can be no love.
Unless you fall in love first, then you have a teacher-student relationship.
In the relationship between teachers and students, only when they are separated from learning can they be considered out of line. In other words, don't communicate anything except study.
In other words, once communication goes beyond learning, it is crossing the line.
Teachers can supervise students to study hard, all for the sake of learning. If students can't study because of troubles, then teachers can enlighten them, but only if they concentrate on their studies or let them return to their studies, unless they go beyond the boundaries.